Figure 17: Signal Characterizer Curve - Honeywell ST700 User Manual

To derive the output value that corresponds to the input, use the following formula,
y = mx + c
Where,
•
m is the slope of the line.
•
c is the y-intercept of the line

Figure 17: Signal characterizer curve

The values of x must increase sequentially for interpolation to be applicable. If not, a
configuration error is set in BLOCK_ERR, and the Actual mode of the block goes to Out
of Service mode.
If the curve has m points, m<21, the non-configured points, [xm+1; ym+1], [xm+2; ym+2],
... [x21; y21] is set to +INFINITY to mark them as unused.
Since x1 is the smallest specified value for the input and x is the largest, the output is at y1
m
when the input is smaller than x1, and the output is at y when the input is larger than x .
m m
Since the ends of the y curve act as limits, the OUT status is shown when either limit is
active.
Backward Control path
A reverse function swaps the interpretation of IN_2 and OUT_2 that provides a way to do
reverse calculation using the same curve. If the parameter SWAP_2 is set to True, the
block provides:
IN_1 = x and OUT_1 = y while IN_2 = y and OUT_2 = x
If the function is not sequential in y and SWAP_2 is True, BLOCK_ERR indicates a
configuration error, and the Actual mode goes to Out of Service mode for x. A function is
said to be sequential when y values always increase or decrease when x values increase.
If SWAP_2 = False, IN_1 and IN_2 have the same engineering units defined in
X_RANGE and OUT_1 and OUT_2 use the units defined in Y_RANGE.
If SWAP_2 = True, OUT _1 and IN_2 have Y_RANGE and OUT_2 and IN_1 have
X_RANGE.
Page 84 FOUNDATION Fieldbus ST 700 Pressure Transmitter User's Guide Revision 2.0